Systems, apparatuses, and methods for broadcast arithmetic operations

ABSTRACT

Embodiments of systems, apparatuses, and methods for instruction execution. In some embodiments, an instruction has fields for a first and a second source operand, and a destination operand. When executed, the instruction causes an arithmetic operation on broadcasted packed data elements of the first source operand and storage of results of each arithmetic operation in the destination operand, wherein the packed data elements of the first source operand to be broadcast are dictated by values of packed data elements stored in a second source operand, wherein the arithmetic operation is defined by the instruction.

FIELD OF INVENTION

The field of invention relates generally to computer processorarchitecture, and, more specifically, to instructions which whenexecuted cause a particular result.

BACKGROUND

Vectorization of sparse update pattern using a conflict detectionpackage has its limitations. Consider an example code of sparse update:

  for(i=0; i<N; i++){   A[idx[i]] += B[i] }

This loop cannot be vectorized with a straightforward approach becauseit may have potential data dependencies when idx[i] has equal values ondifferent iterations of the loop (referencing to the same memoryaddress).

A conventional way to vectorize the loop is to check for conflicts ofindexes with a conflict instruction that generates a result of comparingeach index in a vector to each other, and based on this result valuesare loaded from B[ ] to a vector, permuted, accumulated, and stored toA[ ]. Accumulation is usually done in an inner while loop by permutingvalues based on a special permute control, which is generated based onthe conflict result. This process is iterative and repeated as shownbelow:

  zmm_A = Gather (A + zmm_index); zmm1 = VCONFLICT(zmm_index);zmm_control = generate_perm_control(zmm1); mask_completion = full_mask;while(mask_completion!=0){  mask_todo = compute_new_mask_todo (mask_completion, mask_todo)  zmm_values = Permute(zmm_values,zmm_control)  zmm_res = Add(zmm_res, zmm_values)  mask_todo =compute_new_mask_completion  (mask_completion, mask_todo) } zmm_A =VADD(zmm_A, zmm_res); Scatter (A, zmm_A, zmm_index);

The body and number of iterations of the inner while loop vary dependingon the instruction set available and algorithm implementation. Forexample, if there are 16 equal indexes (corner case), then a simplealgorithm implies 15 permutations and 15 additions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements and in which:

FIG. 1 illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction;

FIG. 2(A) illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction;

FIG. 2(B) illustrates an example of a triangle mask;

FIG. 3 illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction;

FIG. 4 illustrates an exemplary execution of a broadcast addinstruction. Of course, other arithmetic operations may be performed;

FIG. 5 illustrates an exemplary execution of a broadcast addinstruction;

FIG. 6 illustrates an exemplary execution of a broadcast arithinstruction;

FIG. 7 illustrates an embodiment of hardware to process an instructionsuch as a broadcast arith instruction;

FIG. 8 illustrates an embodiment of method performed by a processor toprocess a broadcast arithmetic instruction;

FIGS. 9A-9B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention;

FIG. 10A is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention;

FIG. 10B is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the full opcodefield 974 according to one embodiment of the invention;

FIG. 10C is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the register indexfield 944 according to one embodiment of the invention;

FIG. 10D is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the augmentationoperation field 950 according to one embodiment of the invention;

FIG. 11 is a block diagram of a register architecture 1100 according toone embodiment of the invention;

FIG. 12A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention;

FIG. 12B is a block diagram illustrating both an exemplary embodiment ofan in-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention;

FIGS. 13A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip;

FIG. 14 is a block diagram of a processor 1400 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention;

FIG. 15 shown a block diagram of a system in accordance with oneembodiment of the present invention;

FIG. 16 is a block diagram of a first more specific exemplary system inaccordance with an embodiment of the present invention;

FIG. 17 is a block diagram of a second more specific exemplary system inaccordance with an embodiment of the present invention;

FIG. 18 is a block diagram of a SoC in accordance with an embodiment ofthe present invention; and

FIG. 19 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Unfortunately, typical solutions to the vectorization of a sparse updatepattern necessarily have this loop with permutations and maskcomputations. The most problematic cases are with a large number ofconflicts, which may result in slower code than scalar execution.Detailed herein are embodiments of an instruction to broadcast values toa set of temporal vectors with zeroing unset elements, and then do areduction (addition) of all temporal vectors to a single one. Forexample, in the above code, the set of masks generated by the conflictinstruction are used for sparse reduction operation to a set of temporalvectors with zeroing unset elements.

Some exemplary advantage of using this instruction in a sparse updatepattern may include, but are not limited to: no permutations; nooverhead for generating permute control; no overhead for maskcomputations; and/or no inner while loop at all. The entire while loopcan be replaced by a single instruction detailed herein.

Detailed herein are embodiments a broadcast arithmetic instruction. Theexecution of this instruction causes an execution circuit (executionunit) to perform an arithmetic operation on of broadcasted packed dataelements of a first source and store the result of each of the sums in adestination. In some embodiments, the packed data elements of the firstsource to be broadcast are dictated by values of packed data elements (amask) stored in a second source. In other embodiments, the packed dataelements of the first source to be subjected to the arithmetic aredictated by values of packed data elements (the mask) stored in a secondsource. For example, for each packed data element position of thedestination operand, data from each bit position of corresponding packeddata element of the second source operand is used as an index into apacked data element position of the first source operand, a sum of eachvalue from each indexed packed data element of the first source operandis generated, and the sum is stored into the packed data elementposition of the destination operand. In some embodiments, an initialvalue from the destination is another input used in the arithmeticoperation. As such, an improvement to a computer (processor) itself isdescribed. Note for some arithmetic operations (e.g., add), when usingthe mask, a zero is used in place of a packed data element not used, butfor other arithmetic operations (e.g., multiplication), a one is used inplace of a packed data element not used. Which approach zeroing or one,may be set by the opcode of the instruction.

With this instruction, the algorithm for vectorizing a sparse updatepattern looks like:

   zmm_A = Gather (A + zmm_index)  zmm_mask = VCONFLICT_SQR(zmm_index) /*all-to-all check including self- check, this is a set of masksdetermining elements in groups of unique indexes */  zmm_res =BROADCASTADD  (zmm_mask, zmm_values)  /*do sum i=0..KL-1 of broadcasted(zeroing mode) of zmm_values[i] with a mask zmm_mask[i] */  zmm_A =VADD(zmm_A, zmm_res) //  add result to zmm_A  Scatter (A, zmm_A,zmm_index) //  perform scatter without a mask

FIG. 1 illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction. Note that each vertical columnis the same lane of a vector register. Additionally, while an add(summation) is shown, any arithmetic operation may be performed. Asshown, a packed data source 1 101 will supply packed data elements to beadded. The “offset” refers to each packed data element position of thepacked data source 1 101. In this example, there are 8 (KL=8) packeddata elements.

A packed data index 107 for is a source operand for a conflictinstruction. The result of the conflict instruction generates a packeddata source 2 103 which is used to index packed data element positionsof the packed data source 1 101. Using the index, a plurality oftemporary values (tmp0-7) are generated from broadcasted packed dataelements from the packed data source 1 101.

At each packed data element position of the packed data destination 131,a sum of the broadcasted elements at that position are stored.

FIG. 2(A) illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction. Note that each vertical columnis the same lane of a vector register. Additionally, while an add(summation) is shown, any arithmetic operation may be performed. Asshown, a packed data source 2 201 will supply packed data elements to beadded. The “offset” refers to each packed data element position of thepacked data source 1 201. In this example, there are 8 (KL=8) packeddata elements.

A packed data index 207 is a source operand for a conflict instruction.The result of the conflict instruction is passed used as a source of anAND instruction along with a triangle mask (ZMM_MASK in FIG. 2(B)). Theresult of the AND instruction is a packed data source 2 203 which isused to index packed data element positions of the packed data source 1201. Using the index, a plurality of temporary values (tmp0-7) to addare generated from broadcasted packed data elements from the packed datasource 1 201.

At each packed data element position of the packed data destination 231,a sum of the broadcasted elements at that position are stored.

FIG. 3 illustrates an embodiment of an execution of a broadcast addinstruction after a conflict instruction. Note that each vertical columnis the same lane of a vector register. Additionally, while an add(summation) is shown, any arithmetic operation may be performed. Asshown, a packed data source 2 301 will supply packed data elements to beadded. The “offset” refers to each packed data element position of thepacked data source 1 301. In this example, there are 8 (KL=8) packeddata elements.

A packed data index 307 is a source operand for a triangle conflictinstruction. The result of the conflict instruction is passed used as asource of a triangle conflict instruction. The triangle conflictperforms a comparison of each element to all leftmost elements. Theresult of the triangle conflict instruction is a packed data source 2303 which is used to index packed data element positions of the packeddata source 1 301. Using the index, a plurality of temporary values(tmp0-7) to add are generated from broadcasted packed data elements fromthe packed data source 1 301.

At each packed data element position of the packed data destination 331,a sum of the broadcasted elements at that position are stored.

FIG. 4 illustrates an exemplary execution of a broadcast addinstruction. Of course, other arithmetic operations may be performed.While this illustration is in little endian format, the principlesdiscussed herein work in big endian format. Further, in this example,each packed data element position of the packed data destination 431does not include an original value of stored in that position. Thebroadcast add instruction includes fields for a destination (packed datadestination (DST) 431) and two sources (packed data source 1 (SRC1) 401and packed data source 2 (SRC2) 403).

Packed data source 1 401 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 1 401 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

Packed data source 2 403 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 2 403 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

The two packed data sources 401, 403 are fed into execution circuitry409 to be operated on. In particular, execution circuitry 409 performssums broadcasted packed data elements of a first packed data source 401and stores the result of the sums in packed data destination 431.Wherein in some embodiments, which packed data elements of the firstpacked data source 401 are broadcast are dictated by values of packeddata elements (a mask) stored in a second packed data source 403.Selection and broadcast circuitry 411 uses the packed data elements ofthe packed data source 403 to select how broadcasted packed dataelements of packed data source 1 401 are to be used by one or more addercircuits 421, 423, 425, 427. Note while a plurality of adders is shown,in some embodiments, the same adder is reused. Adders 421, 423, 425, 427add its input packed data element values and the output of each adder421, 423, 425, 427 is placed into a corresponding packed data elementposition of the packed data destination 431. In some embodiments,selection and broadcast circuitry 411 is a configurable crossbar.

As such, as illustrated, for each packed data element position of packeddata destination operand 431, there is an adder that takes in packeddata elements from packed data source 1 401 based on the index providedby the packed data elements of packed data source 2 403. For example, inpacked data element position 0 of packed data source 2 403 the value is0x1. As such, only one bit position (the least significant) is set inthis element. This set bit indicates that for packed data elementposition 0 of packed data source 1 401 that the value in this position(A) is to be added by only one adder (in this example, that addercorresponds to adder[0] 427 which is the adder in the same “position” asthe set bit). In packed data element position 3 of packed data source 2403 the value is 0x6. As such, only 2 bits are set in this element(0b0110). These set bits indicate that for packed data element position3 of packed data source 1 401 that the value in this position (D) is tobe added by the two adders that correspond to the set bit positions (inthis example, those adders corresponds to adder[1] 425 and adder [2]423). The results of the adders are stored into a corresponding packeddata element position of the packed data destination 431 as shown.

FIG. 5 illustrates an exemplary execution of a broadcast addinstruction. While this illustration is in little endian format, theprinciples discussed also work in big endian format. Further, in thisexample, each packed data element position of the packed datadestination 531 does not include an original value of stored in thatposition. The broadcast add instruction includes fields for adestination (packed data destination (DST) 531) and two sources (packeddata source 1 (SRC1) 401 and packed data source 2 (SRC2) 403).

Packed data source 1 401 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 1 401 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

Packed data source 2 403 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 2 403 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

The two packed data sources 401, 403 are fed into execution circuitry509 to be operated on. In particular, execution circuitry 509 performsums of broadcasted packed data elements of a first packed data source401 and stores the result of the sums in packed data destination 531. Insome embodiments, the packed data elements of the first packed datasource 401 are broadcast are dictated by values of packed data elements(a mask) stored in a second packed data source 403. In otherembodiments, the packed data elements of the first packed data source401 are selected after broadcast as dictated by values of packed dataelements (a mask) stored in a second packed data source 403. Selectionand broadcast circuitry 411 uses the packed data elements of the packeddata source 403 to select how packed data elements of packed data source1 401 are broadcast to one or more adder circuits 521, 523, 525, 527.Note while a plurality of adders is shown, in some embodiments, the sameadder is reused. Adders 521, 523, 525, 527 add its input packed dataelement values and a data element from a corresponding packed elementposition of packed data destination 531, and the output of each adder521, 523, 525, 527 is placed into a corresponding packed data elementposition of packed data destination 531. In some embodiments, selectionand broadcast circuitry 411 is a configurable crossbar.

As such, as illustrated, for each packed data element position of packeddata destination operand 531, there is an adder that adds in packed dataelements from packed data source 1 401 based on the index provided bythe packed data elements of packed data source 2 403, and also takes inan initial value from packed data destination 531. For example, inpacked data element position 0 of packed data source 2 403 the value is0x1. As such, only one bit position (the least significant) is set inthis element. This set bit indicates that for packed data elementposition 0 of packed data source 1 401 the value in this position (A) isto be used by only one adder (in this example, that adder corresponds toadder[0] 527 which is the adder in the same “position” as the set bit).In packed data element position 3 of packed data source 2 403 the valueis 0x6. As such, only 2 bits are set in this element (0b0110). These setbits indicate that for packed data element position 3 of packed datasource 1 401 that the value in this position (D) is to be used by thetwo adders that correspond to the set bit positions (in this example,those adders corresponds to adder[1] 525 and adder [2] 523). The resultsof the adders are added to a corresponding packed data element positionof the packed data destination 531 as shown.

FIG. 6 illustrates an exemplary execution of a broadcast arithinstruction. While this illustration is in little endian format, theprinciples discussed also work in big endian format. Further, in thisexample, each packed data element position of the packed datadestination 631 does not include an original value of stored in thatposition. The broadcast arith instruction includes fields for adestination (packed data destination (DST) 631) and two sources (packeddata source 1 (SRC1) 601 and packed data source 2 (SRC2) 603).

Packed data source 1 601 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 1 601 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

Packed data source 2 603 includes four packed data elements (shown atpacked data element positions 0-3). Depending upon the implementation,packed data source 2 603 is a packed data register (e.g., a XMM, YMM,ZMM, vector, SIMD, D, S, etc. register), or a memory location.

The two packed data sources 601, 603 are fed into execution circuitry609 to be operated on. In particular, execution circuitry 609 performsarithmetic operations on selected broadcasted packed data elements of afirst packed data source 601 and stores the results in packed datadestination 631. In some embodiments, the packed data elements of thefirst packed data source 601 are broadcast are dictated by values ofpacked data elements (a mask) stored in a second packed data source 603.In some embodiments, the packed data elements of the first packed datasource 601 are broadcast and then selected as dictated by values ofpacked data elements (a mask) stored in a second packed data source 603.Selection and broadcast circuitry 611 uses the packed data elements ofthe packed data source 603 to select how packed data elements of packeddata source 1 601 are given to one or more arithmetic circuit circuits621, 623, 625, 627. Note while a plurality of arithmetic circuits isshown, in some embodiments, the same arithmetic circuit is reused.Arithmetic circuits 621, 623, 625, 627 perform the operation their inputpacked data element values and a data element from a correspondingpacked element position of packed data destination 631, and the outputof each arithmetic circuit 621, 623, 625, 627 is placed into acorresponding packed data element position of packed data destination631. In some embodiments, selection (and broadcast) circuitry 611 is aconfigurable crossbar.

As such, as illustrated, for each packed data element position of packeddata destination operand 631, there is an arithmetic circuit thatoperates on packed data elements from packed data source 1 601 based onthe index provided by the packed data elements of packed data source 2603. In some embodiments, an initial value from packed data destination631 is also used in the operation. For example, in packed data elementposition 0 of packed data source 2 603 the value is 0x1. As such, onlyone bit position (the least significant) is set in this element. Thisset bit indicates that for packed data element position 0 of packed datasource 1 601 the value in this position (A) is to be used by only onearithmetic circuit (in this example, that arithmetic circuit correspondsto arithmetic circuit[0] 627 which is the arithmetic circuit in the same“position” as the set bit). In packed data element position 3 of packeddata source 2 603 the value is 0x6. As such, only 2 bits are set in thiselement (0b0110). These set bits indicate that for packed data elementposition 3 of packed data source 1 601 that the value in this position(D) is to be used by the two arithmetic circuits that correspond to theset bit positions (in this example, those arithmetic circuitscorresponds to arithmetic circuit[1] 625 and arithmetic circuit [2]623). The results of the arithmetic circuits are added to acorresponding packed data element position of the packed datadestination 631 as shown.

FIG. 7 illustrates an embodiment of hardware to process an instructionsuch as a broadcast arith instruction. As illustrated, storage 703stores a broadcast arith instruction 701 to be executed.

The instruction 701 is received by decode circuitry 705. For example,the decode circuitry 705 receives this instruction from fetchlogic/circuitry. The instruction includes fields for an opcode, firstand second sources, and a destination. In some embodiments, the sourcesand destination are registers, and in other embodiments one or more arememory locations. In some embodiments, an opcode or prefix of theinstruction 701 includes an indication of data element size {B/W/D/Q}for element sizes of byte, word, doubleword, and quadword.

More detailed embodiments of at least one instruction format will bedetailed later. The decode circuitry 705 decodes the instruction intoone or more operations. In some embodiments, this decoding includesgenerating a plurality of micro-operations to be performed by executioncircuitry (such as execution circuitry 709). The decode circuitry 705also decodes instruction prefixes.

In some embodiments, register renaming, register allocation, and/orscheduling circuitry 707 provides functionality for one or more of: 1)renaming logical operand values to physical operand values (e.g., aregister alias table in some embodiments), 2) allocating status bits andflags to the decoded instruction, and 3) scheduling the decodedinstruction for execution on execution circuitry out of an instructionpool (e.g., using a reservation station in some embodiments).

Registers (register file) and/or memory 708 store data as operands ofthe instruction to be operated on by execution circuitry 709. Exemplaryregister types include packed data registers, general purpose registers,and floating point registers.

Execution circuitry 709 executes the decoded instruction. Exemplarydetailed execution circuitry was shown in FIGS. 4-6. The execution ofthe decoded instruction causes the execution circuitry to perform anarithmetic operation on broadcasted packed data elements of a firstsource and store the result of the arithmetic operation in adestination. In some embodiments, the packed data elements of the firstsource to be broadcast are dictated by values of packed data elements (amask) stored in a second source. In other embodiments, the mask is usedto dictate which elements are subject to reduction. For example, foreach packed data element position of the destination operand, data fromeach bit position of corresponding packed data element of the secondsource operand is used as an index into a packed data element positionof the first source operand, generate a result of an arithmeticoperation (e.g., sum, subtraction, multiplication, division) of eachvalue from each indexed packed data element of the first source operand,and store the result of the arithmetic operation into the packed dataelement position of the destination operand. In some embodiments, aninitial value from the destination is another input used in theoperation (e.g., sum generation).

In some embodiments, retirement/write back circuitry 711 architecturallycommits the destination register into the registers or memory 708 andretires the instruction.

An embodiment of a format for a broadcast add instruction is BROADCASTARITH{B/W/D/Q} DSTREG, SRC1, SRC2. In some embodiments, BROADCASTARITH{B/W/D/Q} is the opcode mnemonic of the instruction. ARITH is thearithmetic function to be performed such as ADD (addition), SUB(subtraction), MUL (multiplication), DIV (division), etc. B/W/D/Qindicates the data element sizes of the sources/destination as byte,word, doubleword, and quadword. In other embodiments, the data elementsize is a part of a prefix. DSTREG is a field for the packed datadestination register operand. SRC1 and SRC2 are fields for the sourcessuch as packed data registers and/or memory.

In some embodiments, the broadcast arith instruction includes a fieldfor a writemask register operand (k) (e.g., BROADCAST ARITH{B/W/D/Q}{k}DSTREG, SRC1, SRC2). A writemask is used to conditionally controlper-element operations and updating of results. Depending upon theimplementation, the writemask uses merging or zeroing masking.Instructions encoded with a predicate (writemask, write mask, or kregister) operand use that operand to conditionally control per-elementcomputational operation and updating of result to the destinationoperand. The predicate operand is known as the opmask (writemask)register. In some embodiments, the opmask is a set of architecturalregisters of size 64-bit. Note that from this set of architecturalregisters, only k1 through k7 can be addressed as predicate operand. k0can be used as a regular source or destination but cannot be encoded asa predicate operand. Note also that a predicate operand can be used toenable memory fault-suppression for some instructions with a memoryoperand (source or destination). As a predicate operand, the opmaskregisters contain one bit to govern the operation/update to each dataelement of a vector register. In general, opmask registers can supportinstructions with element sizes: single-precision floating-point(float32), integer doubleword (int32), double-precision floating-point(float64), integer quadword (int64). The length of a opmask register,MAX_KL, is sufficient to handle up to 64 elements with one bit perelement, i.e. 64 bits. For a given vector length, each instructionaccesses only the number of least significant mask bits that are neededbased on its data type. An opmask register affects an instruction atper-element granularity. So, any numeric or non-numeric operation ofeach data element and per-element updates of intermediate results to thedestination operand are predicated on the corresponding bit of theopmask register. In most embodiments, an opmask serving as a predicateoperand obeys the following properties: 1) the instruction's operationis not performed for an element if the corresponding opmask bit is notset (this implies that no exception or violation can be caused by anoperation on a masked-off element, and consequently, no exception flagis updated as a result of a masked-off operation); 2). a destinationelement is not updated with the result of the operation if thecorresponding writemask bit is not set. Instead, the destination elementvalue must be preserved (merging-masking) or it must be zeroed out(zeroing-masking); 3) for some instructions with a memory operand,memory faults are suppressed for elements with a mask bit of 0. Notethat this feature provides a versatile construct to implementcontrol-flow predication as the mask in effect provides a mergingbehavior for vector register destinations. As an alternative the maskingcan be used for zeroing instead of merging, so that the masked outelements are updated with 0 instead of preserving the old value. Thezeroing behavior is provided to remove the implicit dependency on theold value when it is not needed.

In embodiments, encodings of the instruction include a scale-index-base(SIB) type memory addressing operand that indirectly identifies multipleindexed destination locations in memory. In one embodiment, an SIB typememory operand may include an encoding identifying a base addressregister. The contents of the base address register may represent a baseaddress in memory from which the addresses of the particular destinationlocations in memory are calculated. For example, the base address may bethe address of the first location in a block of potential destinationlocations for an extended vector instruction. In one embodiment, an SIBtype memory operand may include an encoding identifying an indexregister. Each element of the index register may specify an index oroffset value usable to compute, from the base address, an address of arespective destination location within a block of potential destinationlocations. In one embodiment, an SIB type memory operand may include anencoding specifying a scaling factor to be applied to each index valuewhen computing a respective destination address. For example, if ascaling factor value of four is encoded in the SIB type memory operand,each index value obtained from an element of the index register may bemultiplied by four and then added to the base address to compute adestination address.

In one embodiment, an SIB type memory operand of the form vm32{x,y,z}may identify a vector array of memory operands specified using SIB typememory addressing. In this example, the array of memory addresses isspecified using a common base register, a constant scaling factor, and avector index register containing individual elements, each of which is a32-bit index value. The vector index register may be a 128-bit register(e.g., XMM) register (vm32x), a 256-bit (e.g., YMM) register (vm32y), ora 512-bit (e.g., ZMM) register (vm32z). In another embodiment, an SIBtype memory operand of the form vm64{x,y,z} may identify a vector arrayof memory operands specified using SIB type memory addressing. In thisexample, the array of memory addresses is specified using a common baseregister, a constant scaling factor, and a vector index registercontaining individual elements, each of which is a 64-bit index value.The vector index register may be a 128-bit register (e.g., XMM) register(vm64x), a 256-bit (e.g., YMM) register (vm64y) or a 512-bit (e.g., ZMM)register (vm64z).

FIG. 8 illustrates an embodiment of method performed by a processor toprocess a broadcast arithmetic instruction. For example, a processorcore as shown in FIG. 4-7, a pipeline as detailed below, etc. performsthis method.

At 801, an instruction is fetched. For example, a broadcast arithinstruction is fetched. The broadcast arith instruction includes fieldsfor an opcode, a first and a second source operand, and a destinationoperand. In some embodiments, the instruction further includes a fieldfor a writemask. In some embodiments, the instruction is fetched from aninstruction cache. The source operands and destination operand arepacked data. The opcode indicates which operation is to be performed.

The fetched instruction is decoded at 803. For example, the fetchedbroadcast add instruction is decoded by decode circuitry such as thatdetailed herein.

Data values associated with the source operands of the decodedinstruction are retrieved at 805. For example, when one or more of thesource operands are memory operands, the data from the indicated memorylocation is retrieved.

At 807, the decoded instruction is executed by execution circuitry(hardware) such as that detailed herein. For the broadcast addinstruction, the execution will cause execution circuitry to perform anarithmetic operation on broadcasted packed data elements of the firstsource operand and store the results of each sum in the destinationoperand. In some embodiments, the packed data elements of the firstsource operand to be broadcast are dictated by values of packed dataelements (a mask) stored in a second source operand. In otherembodiments, the broadcasted packed data elements of the first sourceoperand to be selected for the operation are dictated by values ofpacked data elements (a mask) stored in a second source operand. Forexample, for each packed data element position of the destinationoperand, data from each bit position of corresponding packed dataelement of the second source operand is used as an index into a packeddata element position of the first source operand, a result theoperation of each value from each indexed packed data element of thefirst source operand, and the result is stored into the packed dataelement position of the destination operand. In some embodiments, aninitial value from the destination is another input used in the sumgeneration.

In some embodiments, the instruction is committed or retired at 809.

An example of pseudocode for broadcast add is as follows:

  BROADCASTADD dest, src1, src2 tmp[KL-1:0]=0   for(i=0; i<KL; i++){   kmask[KL-1:0] = src2[i][KL-1:0]    //src2[i] is a vector of KL bits   value = src1[i]    for(j=0; j<KL; j++){     if(kmask[j]) tmp[j] +=value   }  } dest[KL-1:0] = tmp[KL-1:0]

KL is number of elements given for reduction in the input source 1vector. While the reduction is shown as a serialized sequence ofaccumulation in one temporal vector, but in other implementation it canbe done through KL temporal vectors (thus, broadcast operations areparallelized) with reduction performed by a tree.

Examples of embodiments are detailed below.

1. An apparatus comprising a decoder to decode an instruction havingfields for a first and a second source operand, and a destinationoperand, and execution circuitry to execute the decoded instruction toperform an arithmetic operation on broadcasted packed data elements ofthe first source operand and store results of each arithmetic operationin the destination operand, wherein the packed data elements of thefirst source operand to be broadcast are dictated by values of packeddata elements stored in a second source operand, wherein the arithmeticoperation is defined by the instruction.

2. The apparatus of example 1, wherein the first source operand is apacked data register and the second source operand is a memory location.

3. The apparatus of example 1, wherein the first source operand is apacked data register and the second source operand is a packed dataregister.

4. The apparatus of example 1, wherein the values of packed dataelements stored in the second source operand form a mask.

5. The apparatus of example 1, wherein to execute the decodedinstruction, the execution circuitry is to, for each packed data elementposition of the destination operand, use data from each bit position ofcorresponding packed data element of the second source operand as anindex into a packed data element position of the first source operand,generate a result of the arithmetic operation of each value from eachindexed packed data element of the first source operand, and store theresult into the packed data element position of the destination operand.

6. The apparatus of example 1, wherein the arithmetic operation is oneof addition, subtraction, multiplication, and division.

7. The apparatus of example 1, wherein the apparatus to translate theinstruction from a first instruction set into an instruction of a secondinstruction set prior to a decode, wherein the instruction to be decodedis of the second instruction set.

8. An method comprising decoding an instruction having fields for afirst and a second source operand, and a destination operand, andexecuting the decoded instruction to sum broadcasted packed dataelements of the first source operand and store results of each sum inthe destination operand, wherein the packed data elements of the firstsource operand to be broadcast are dictated by values of packed dataelements stored in a second source operand.

9. The method of example 8, wherein the first source operand is a packeddata register and the second source operand is a memory location.

10. The method of example 8, wherein the first source operand is apacked data register and the second source operand is a packed dataregister.

11. The method of example 8, wherein the values of packed data elementsstored in the second source operand form a mask.

12. The method of example 8, wherein for each packed data elementposition of the destination operand, using data from each bit positionof corresponding packed data element of the second source operand as anindex into a packed data element position of the first source operand,generating a sum of each value from each indexed packed data element ofthe first source operand, and storing the sum into the packed dataelement position of the destination operand.

13. The method of example 8, wherein an initial value from thedestination is another input used in the sum generation.

14. The method of example 8, further comprising: translating theinstruction from a first instruction set into an instruction of a secondinstruction set prior to a decode, wherein the instruction to be decodedis of the second instruction set.

15. A non-transitory machine-readable medium storing an instructionwhich when executed by a processor causes the processor to perform amethod, the method comprising decoding an instruction having fields fora first and a second source operand, and a destination operand, andexecuting the decoded instruction to sum broadcasted packed dataelements of the first source operand and store results of each sum inthe destination operand, wherein the packed data elements of the firstsource operand to be broadcast are dictated by values of packed dataelements stored in a second source operand.

16. The non-transitory machine-readable medium of example 15, whereinthe first source operand is a packed data register and the second sourceoperand is a memory location.

17. The non-transitory machine-readable medium of example 15, whereinthe first source operand is a packed data register and the second sourceoperand is a packed data register.

18. The non-transitory machine-readable medium of example 15, whereinthe values of packed data elements stored in the second source operandform a mask.

19. The non-transitory machine-readable medium of example 15, whereinfor each packed data element position of the destination operand, usingdata from each bit position of corresponding packed data element of thesecond source operand as an index into a packed data element position ofthe first source operand, generating a sum of each value from eachindexed packed data element of the first source operand, and storing thesum into the packed data element position of the destination operand.

20. The non-transitory machine-readable medium of example 15, wherein aninitial value from the destination is another input used in the sumgeneration.

21. The non-transitory machine-readable medium of example 15, furthercomprising: translating the instruction from a first instruction setinto an instruction of a second instruction set prior to a decode,wherein the instruction to be decoded is of the second instruction set.

22. An apparatus comprising decoder means for decoding an instructionhaving fields for a first and a second source operand, and a destinationoperand, and execution means for executing the decoded instruction toperform an arithmetic operation on broadcasted packed data elements ofthe first source operand and store results of each arithmetic operationin the destination operand, wherein the packed data elements of thefirst source operand to be broadcast are dictated by values of packeddata elements stored in a second source operand, wherein the arithmeticoperation is defined by the instruction.

23. The apparatus of example 22, wherein the first source operand is apacked data register and the second source operand is a memory location.

24. The apparatus of example 22, wherein the first source operand is apacked data register and the second source operand is a packed dataregister.

25. The apparatus of any of examples 22-24, wherein the values of packeddata elements stored in the second source operand form a mask.

26. The apparatus of any of examples 22-25, wherein to execute thedecoded instruction, the execution means is to, for each packed dataelement position of the destination operand, use data from each bitposition of corresponding packed data element of the second sourceoperand as an index into a packed data element position of the firstsource operand, generate a result of the arithmetic operation of eachvalue from each indexed packed data element of the first source operand,and store the result into the packed data element position of thedestination operand.

27. The apparatus of any of examples 22-26, wherein the arithmeticoperation is one of addition, subtraction, multiplication, and division.

28. The apparatus of any of examples 22-27, wherein the apparatus totranslate the instruction from a first instruction set into aninstruction of a second instruction set prior to a decode, wherein theinstruction to be decoded is of the second instruction set.

The figures below detail exemplary architectures and systems toimplement embodiments of the above. In some embodiments, one or morehardware components and/or instructions described above are emulated asdetailed below, or implemented as software modules.

Instruction Sets

An instruction set may include one or more instruction formats. A giveninstruction format may define various fields (e.g., number of bits,location of bits) to specify, among other things, the operation to beperformed (e.g., opcode) and the operand(s) on which that operation isto be performed and/or other data field(s) (e.g., mask). Someinstruction formats are further broken down though the definition ofinstruction templates (or subformats). For example, the instructiontemplates of a given instruction format may be defined to have differentsubsets of the instruction format's fields (the included fields aretypically in the same order, but at least some have different bitpositions because there are less fields included) and/or defined to havea given field interpreted differently. Thus, each instruction of an ISAis expressed using a given instruction format (and, if defined, in agiven one of the instruction templates of that instruction format) andincludes fields for specifying the operation and the operands. Forexample, an exemplary ADD instruction has a specific opcode and aninstruction format that includes an opcode field to specify that opcodeand operand fields to select operands (source1/destination and source2);and an occurrence of this ADD instruction in an instruction stream willhave specific contents in the operand fields that select specificoperands. A set of SIMD extensions referred to as the Advanced VectorExtensions (AVX) (AVX1 and AVX2) and using the Vector Extensions (VEX)coding scheme has been released and/or published (e.g., see Intel® 64and IA-32 Architectures Software Developer's Manual, September 2014; andsee Intel® Advanced Vector Extensions Programming Reference, October2014).

Exemplary Instruction Formats

Embodiments of the instruction(s) described herein may be embodied indifferent formats. Additionally, exemplary systems, architectures, andpipelines are detailed below. Embodiments of the instruction(s) may beexecuted on such systems, architectures, and pipelines, but are notlimited to those detailed.

Generic Vector Friendly Instruction Format

A vector friendly instruction format is an instruction format that issuited for vector instructions (e.g., there are certain fields specificto vector operations). While embodiments are described in which bothvector and scalar operations are supported through the vector friendlyinstruction format, alternative embodiments use only vector operationsthe vector friendly instruction format.

FIGS. 9A-9B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention. FIG. 9A is a block diagram illustrating ageneric vector friendly instruction format and class A instructiontemplates thereof according to embodiments of the invention; while FIG.9B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention. Specifically, a generic vector friendlyinstruction format 900 for which are defined class A and class Binstruction templates, both of which include no memory access 905instruction templates and memory access 920 instruction templates. Theterm generic in the context of the vector friendly instruction formatrefers to the instruction format not being tied to any specificinstruction set.

While embodiments of the invention will be described in which the vectorfriendly instruction format supports the following: a 64 byte vectoroperand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) dataelement widths (or sizes) (and thus, a 64 byte vector consists of either16 doubleword-size elements or alternatively, 8 quadword-size elements);a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit(1 byte) data element widths (or sizes); a 32 byte vector operand length(or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8bit (1 byte) data element widths (or sizes); and a 16 byte vectoroperand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit(2 byte), or 8 bit (1 byte) data element widths (or sizes); alternativeembodiments may support more, less and/or different vector operand sizes(e.g., 256 byte vector operands) with more, less, or different dataelement widths (e.g., 128 bit (16 byte) data element widths).

The class A instruction templates in FIG. 9A include: 1) within the nomemory access 905 instruction templates there is shown a no memoryaccess, full round control type operation 910 instruction template and ano memory access, data transform type operation 915 instructiontemplate; and 2) within the memory access 920 instruction templatesthere is shown a memory access, temporal 925 instruction template and amemory access, non-temporal 930 instruction template. The class Binstruction templates in FIG. 9B include: 1) within the no memory access905 instruction templates there is shown a no memory access, write maskcontrol, partial round control type operation 912 instruction templateand a no memory access, write mask control, vsize type operation 917instruction template; and 2) within the memory access 920 instructiontemplates there is shown a memory access, write mask control 927instruction template.

The generic vector friendly instruction format 900 includes thefollowing fields listed below in the order illustrated in FIGS. 9A-9B.

Format field 940—a specific value (an instruction format identifiervalue) in this field uniquely identifies the vector friendly instructionformat, and thus occurrences of instructions in the vector friendlyinstruction format in instruction streams. As such, this field isoptional in the sense that it is not needed for an instruction set thathas only the generic vector friendly instruction format.

Base operation field 942—its content distinguishes different baseoperations.

Register index field 944—its content, directly or through addressgeneration, specifies the locations of the source and destinationoperands, be they in registers or in memory. These include a sufficientnumber of bits to select N registers from a P×Q (e.g. 32×512, 16×128,32×1024, 64×1024) register file. While in one embodiment N may be up tothree sources and one destination register, alternative embodiments maysupport more or less sources and destination registers (e.g., maysupport up to two sources where one of these sources also acts as thedestination, may support up to three sources where one of these sourcesalso acts as the destination, may support up to two sources and onedestination).

Modifier field 946—its content distinguishes occurrences of instructionsin the generic vector instruction format that specify memory access fromthose that do not; that is, between no memory access 905 instructiontemplates and memory access 920 instruction templates. Memory accessoperations read and/or write to the memory hierarchy (in some casesspecifying the source and/or destination addresses using values inregisters), while non-memory access operations do not (e.g., the sourceand destinations are registers). While in one embodiment this field alsoselects between three different ways to perform memory addresscalculations, alternative embodiments may support more, less, ordifferent ways to perform memory address calculations.

Augmentation operation field 950—its content distinguishes which one ofa variety of different operations to be performed in addition to thebase operation. This field is context specific. In one embodiment of theinvention, this field is divided into a class field 968, an alpha field952, and a beta field 954. The augmentation operation field 950 allowscommon groups of operations to be performed in a single instructionrather than 2, 3, or 4 instructions.

Scale field 960—its content allows for the scaling of the index field'scontent for memory address generation (e.g., for address generation thatuses 2^(scale)*index+base).

Displacement Field 962A—its content is used as part of memory addressgeneration (e.g., for address generation that uses2^(scale)*index+base+displacement).

Displacement Factor Field 962B (note that the juxtaposition ofdisplacement field 962A directly over displacement factor field 962Bindicates one or the other is used)—its content is used as part ofaddress generation; it specifies a displacement factor that is to bescaled by the size of a memory access (N)—where N is the number of bytesin the memory access (e.g., for address generation that uses2^(scale)*index+base+scaled displacement). Redundant low-order bits areignored and hence, the displacement factor field's content is multipliedby the memory operands total size (N) in order to generate the finaldisplacement to be used in calculating an effective address. The valueof N is determined by the processor hardware at runtime based on thefull opcode field 974 (described later herein) and the data manipulationfield 954C. The displacement field 962A and the displacement factorfield 962B are optional in the sense that they are not used for the nomemory access 905 instruction templates and/or different embodiments mayimplement only one or none of the two.

Data element width field 964—its content distinguishes which one of anumber of data element widths is to be used (in some embodiments for allinstructions; in other embodiments for only some of the instructions).This field is optional in the sense that it is not needed if only onedata element width is supported and/or data element widths are supportedusing some aspect of the opcodes.

Write mask field 970—its content controls, on a per data elementposition basis, whether that data element position in the destinationvector operand reflects the result of the base operation andaugmentation operation. Class A instruction templates supportmerging-writemasking, while class B instruction templates support bothmerging- and zeroing-writemasking. When merging, vector masks allow anyset of elements in the destination to be protected from updates duringthe execution of any operation (specified by the base operation and theaugmentation operation); in other one embodiment, preserving the oldvalue of each element of the destination where the corresponding maskbit has a 0. In contrast, when zeroing vector masks allow any set ofelements in the destination to be zeroed during the execution of anyoperation (specified by the base operation and the augmentationoperation); in one embodiment, an element of the destination is set to 0when the corresponding mask bit has a 0 value. A subset of thisfunctionality is the ability to control the vector length of theoperation being performed (that is, the span of elements being modified,from the first to the last one); however, it is not necessary that theelements that are modified be consecutive. Thus, the write mask field970 allows for partial vector operations, including loads, stores,arithmetic, logical, etc. While embodiments of the invention aredescribed in which the write mask field's 970 content selects one of anumber of write mask registers that contains the write mask to be used(and thus the write mask field's 970 content indirectly identifies thatmasking to be performed), alternative embodiments instead or additionalallow the mask write field's 970 content to directly specify the maskingto be performed.

Immediate field 972—its content allows for the specification of animmediate. This field is optional in the sense that is it not present inan implementation of the generic vector friendly format that does notsupport immediate and it is not present in instructions that do not usean immediate.

Class field 968—its content distinguishes between different classes ofinstructions. With reference to FIGS. 9A-B, the contents of this fieldselect between class A and class B instructions. In FIGS. 9A-B, roundedcorner squares are used to indicate a specific value is present in afield (e.g., class A 968A and class B 968B for the class field 968respectively in FIGS. 9A-B).

Instruction Templates of Class A

In the case of the non-memory access 905 instruction templates of classA, the alpha field 952 is interpreted as an RS field 952A, whose contentdistinguishes which one of the different augmentation operation typesare to be performed (e.g., round 952A.1 and data transform 952A.2 arerespectively specified for the no memory access, round type operation910 and the no memory access, data transform type operation 915instruction templates), while the beta field 954 distinguishes which ofthe operations of the specified type is to be performed. In the nomemory access 905 instruction templates, the scale field 960, thedisplacement field 962A, and the displacement scale filed 962B are notpresent.

No-Memory Access Instruction Templates—Full Round Control Type Operation

In the no memory access full round control type operation 910instruction template, the beta field 954 is interpreted as a roundcontrol field 954A, whose content(s) provide static rounding. While inthe described embodiments of the invention the round control field 954Aincludes a suppress all floating point exceptions (SAE) field 956 and around operation control field 958, alternative embodiments may supportmay encode both these concepts into the same field or only have one orthe other of these concepts/fields (e.g., may have only the roundoperation control field 958).

SAE field 956—its content distinguishes whether or not to disable theexception event reporting; when the SAE field's 956 content indicatessuppression is enabled, a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler.

Round operation control field 958—its content distinguishes which one ofa group of rounding operations to perform (e.g., Round-up, Round-down,Round-towards-zero and Round-to-nearest). Thus, the round operationcontrol field 958 allows for the changing of the rounding mode on a perinstruction basis. In one embodiment of the invention where a processorincludes a control register for specifying rounding modes, the roundoperation control field's 950 content overrides that register value.

No Memory Access Instruction Templates—Data Transform Type Operation

In the no memory access data transform type operation 915 instructiontemplate, the beta field 954 is interpreted as a data transform field954B, whose content distinguishes which one of a number of datatransforms is to be performed (e.g., no data transform, swizzle,broadcast).

In the case of a memory access 920 instruction template of class A, thealpha field 952 is interpreted as an eviction hint field 952B, whosecontent distinguishes which one of the eviction hints is to be used (inFIG. 9A, temporal 952B.1 and non-temporal 952B.2 are respectivelyspecified for the memory access, temporal 925 instruction template andthe memory access, non-temporal 930 instruction template), while thebeta field 954 is interpreted as a data manipulation field 954C, whosecontent distinguishes which one of a number of data manipulationoperations (also known as primitives) is to be performed (e.g., nomanipulation; broadcast; up conversion of a source; and down conversionof a destination). The memory access 920 instruction templates includethe scale field 960, and optionally the displacement field 962A or thedisplacement scale field 962B.

Vector memory instructions perform vector loads from and vector storesto memory, with conversion support. As with regular vector instructions,vector memory instructions transfer data from/to memory in a dataelement-wise fashion, with the elements that are actually transferred isdictated by the contents of the vector mask that is selected as thewrite mask.

Memory Access Instruction Templates—Temporal

Temporal data is data likely to be reused soon enough to benefit fromcaching. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Memory Access Instruction Templates—Non-Temporal

Non-temporal data is data unlikely to be reused soon enough to benefitfrom caching in the 1st-level cache and should be given priority foreviction. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Instruction Templates of Class B

In the case of the instruction templates of class B, the alpha field 952is interpreted as a write mask control (Z) field 952C, whose contentdistinguishes whether the write masking controlled by the write maskfield 970 should be a merging or a zeroing.

In the case of the non-memory access 905 instruction templates of classB, part of the beta field 954 is interpreted as an RL field 957A, whosecontent distinguishes which one of the different augmentation operationtypes are to be performed (e.g., round 957A.1 and vector length (VSIZE)957A.2 are respectively specified for the no memory access, write maskcontrol, partial round control type operation 912 instruction templateand the no memory access, write mask control, VSIZE type operation 917instruction template), while the rest of the beta field 954distinguishes which of the operations of the specified type is to beperformed. In the no memory access 905 instruction templates, the scalefield 960, the displacement field 962A, and the displacement scale filed962B are not present.

In the no memory access, write mask control, partial round control typeoperation 910 instruction template, the rest of the beta field 954 isinterpreted as a round operation field 959A and exception eventreporting is disabled (a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler).

Round operation control field 959A—just as round operation control field958, its content distinguishes which one of a group of roundingoperations to perform (e.g., Round-up, Round-down, Round-towards-zeroand Round-to-nearest). Thus, the round operation control field 959Aallows for the changing of the rounding mode on a per instruction basis.In one embodiment of the invention where a processor includes a controlregister for specifying rounding modes, the round operation controlfield's 950 content overrides that register value.

In the no memory access, write mask control, VSIZE type operation 917instruction template, the rest of the beta field 954 is interpreted as avector length field 959B, whose content distinguishes which one of anumber of data vector lengths is to be performed on (e.g., 128, 256, or512 byte).

In the case of a memory access 920 instruction template of class B, partof the beta field 954 is interpreted as a broadcast field 957B, whosecontent distinguishes whether or not the broadcast type datamanipulation operation is to be performed, while the rest of the betafield 954 is interpreted the vector length field 959B. The memory access920 instruction templates include the scale field 960, and optionallythe displacement field 962A or the displacement scale field 962B.

With regard to the generic vector friendly instruction format 900, afull opcode field 974 is shown including the format field 940, the baseoperation field 942, and the data element width field 964. While oneembodiment is shown where the full opcode field 974 includes all ofthese fields, the full opcode field 974 includes less than all of thesefields in embodiments that do not support all of them. The full opcodefield 974 provides the operation code (opcode).

The augmentation operation field 950, the data element width field 964,and the write mask field 970 allow these features to be specified on aper instruction basis in the generic vector friendly instruction format.

The combination of write mask field and data element width field createtyped instructions in that they allow the mask to be applied based ondifferent data element widths.

The various instruction templates found within class A and class B arebeneficial in different situations. In some embodiments of theinvention, different processors or different cores within a processormay support only class A, only class B, or both classes. For instance, ahigh performance general purpose out-of-order core intended forgeneral-purpose computing may support only class B, a core intendedprimarily for graphics and/or scientific (throughput) computing maysupport only class A, and a core intended for both may support both (ofcourse, a core that has some mix of templates and instructions from bothclasses but not all templates and instructions from both classes iswithin the purview of the invention). Also, a single processor mayinclude multiple cores, all of which support the same class or in whichdifferent cores support different class. For instance, in a processorwith separate graphics and general purpose cores, one of the graphicscores intended primarily for graphics and/or scientific computing maysupport only class A, while one or more of the general purpose cores maybe high performance general purpose cores with out of order executionand register renaming intended for general-purpose computing thatsupport only class B. Another processor that does not have a separategraphics core, may include one more general purpose in-order orout-of-order cores that support both class A and class B. Of course,features from one class may also be implement in the other class indifferent embodiments of the invention. Programs written in a high levellanguage would be put (e.g., just in time compiled or staticallycompiled) into an variety of different executable forms, including: 1) aform having only instructions of the class(es) supported by the targetprocessor for execution; or 2) a form having alternative routineswritten using different combinations of the instructions of all classesand having control flow code that selects the routines to execute basedon the instructions supported by the processor which is currentlyexecuting the code.

Exemplary Specific Vector Friendly Instruction Format

FIG. 10A is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention.FIG. 10A shows a specific vector friendly instruction format 1000 thatis specific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields. The specific vector friendly instruction format 1000 maybe used to extend the x86 instruction set, and thus some of the fieldsare similar or the same as those used in the existing x86 instructionset and extension thereof (e.g., AVX). This format remains consistentwith the prefix encoding field, real opcode byte field, MOD R/M field,SIB field, displacement field, and immediate fields of the existing x86instruction set with extensions. The fields from FIG. 9 into which thefields from FIG. 10A map are illustrated.

It should be understood that, although embodiments of the invention aredescribed with reference to the specific vector friendly instructionformat 1000 in the context of the generic vector friendly instructionformat 900 for illustrative purposes, the invention is not limited tothe specific vector friendly instruction format 1000 except whereclaimed. For example, the generic vector friendly instruction format 900contemplates a variety of possible sizes for the various fields, whilethe specific vector friendly instruction format 1000 is shown as havingfields of specific sizes. By way of specific example, while the dataelement width field 964 is illustrated as a one bit field in thespecific vector friendly instruction format 1000, the invention is notso limited (that is, the generic vector friendly instruction format 900contemplates other sizes of the data element width field 964).

The generic vector friendly instruction format 900 includes thefollowing fields listed below in the order illustrated in FIG. 10A.

EVEX Prefix (Bytes 0-3) 1002—is encoded in a four-byte form.

Format Field 940 (EVEX Byte 0, bits [7:0])—the first byte (EVEX Byte 0)is the format field 940 and it contains 0x62 (the unique value used fordistinguishing the vector friendly instruction format in one embodimentof the invention).

The second-fourth bytes (EVEX Bytes 1-3) include a number of bit fieldsproviding specific capability.

REX field 1005 (EVEX Byte 1, bits [7-5])—consists of a EVEX.R bit field(EVEX Byte 1, bit [7]-R), EVEX.X bit field (EVEX byte 1, bit [6]-X), and957BEX byte 1, bit[5]-B). The EVEX.R, EVEX.X, and EVEX.B bit fieldsprovide the same functionality as the corresponding VEX bit fields, andare encoded using 1s complement form, i.e. ZMM0 is encoded as 1111B,ZMM15 is encoded as 0000B. Other fields of the instructions encode thelower three bits of the register indexes as is known in the art (rrr,xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by addingEVEX.R, EVEX.X, and EVEX.B.

REX′ field 910—this is the first part of the REX′ field 910 and is theEVEX.R′ bit field (EVEX Byte 1, bit [4]-R′) that is used to encodeeither the upper 16 or lower 16 of the extended 32 register set. In oneembodiment of the invention, this bit, along with others as indicatedbelow, is stored in bit inverted format to distinguish (in thewell-known x86 32-bit mode) from the BOUND instruction, whose realopcode byte is 62, but does not accept in the MOD RIM field (describedbelow) the value of 11 in the MOD field; alternative embodiments of theinvention do not store this and the other indicated bits below in theinverted format. A value of 1 is used to encode the lower 16 registers.In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and theother RRR from other fields.

Opcode map field 1015 (EVEX byte 1, bits [3:0]-mmmm)—its content encodesan implied leading opcode byte (0F, 0F 38, or 0F 3).

Data element width field 964 (EVEX byte 2, bit [7]-W)—is represented bythe notation EVEX.W. EVEX.W is used to define the granularity (size) ofthe datatype (either 32-bit data elements or 64-bit data elements).

EVEX.vvvv 1020 (EVEX Byte 2, bits [6:3]-vvvv)—the role of EVEX.vvvv mayinclude the following: 1) EVEX.vvvv encodes the first source registeroperand, specified in inverted (1s complement) form and is valid forinstructions with 2 or more source operands; 2) EVEX.vvvv encodes thedestination register operand, specified in 1s complement form forcertain vector shifts; or 3) EVEX.vvvv does not encode any operand, thefield is reserved and should contain 1111b. Thus, EVEX.vvvv field 1020encodes the 4 low-order bits of the first source register specifierstored in inverted (1s complement) form. Depending on the instruction,an extra different EVEX bit field is used to extend the specifier sizeto 32 registers.

EVEX.U 968 Class field (EVEX byte 2, bit [2]-U)—If EVEX.U=0, itindicates class A or EVEX.U0; if EVEX.U=1, it indicates class B orEVEX.U1.

Prefix encoding field 1025 (EVEX byte 2, bits [1:0]-pp)—providesadditional bits for the base operation field. In addition to providingsupport for the legacy SSE instructions in the EVEX prefix format, thisalso has the benefit of compacting the SIMD prefix (rather thanrequiring a byte to express the SIMD prefix, the EVEX prefix requiresonly 2 bits). In one embodiment, to support legacy SSE instructions thatuse a SIMD prefix (66H, F2H, F3H) in both the legacy format and in theEVEX prefix format, these legacy SIMD prefixes are encoded into the SIMDprefix encoding field; and at runtime are expanded into the legacy SIMDprefix prior to being provided to the decoder's PLA (so the PLA canexecute both the legacy and EVEX format of these legacy instructionswithout modification). Although newer instructions could use the EVEXprefix encoding field's content directly as an opcode extension, certainembodiments expand in a similar fashion for consistency but allow fordifferent meanings to be specified by these legacy SIMD prefixes. Analternative embodiment may redesign the PLA to support the 2 bit SIMDprefix encodings, and thus not require the expansion.

Alpha field 952 (EVEX byte 3, bit [7]-EH; also known as EVEX.EH,EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustratedwith α)—as previously described, this field is context specific.

Beta field 954 (EVEX byte 3, bits [6:4]-SSS, also known as EVEX.s₂₋₀,EVEX.r₂₋₀, EVEX.rr1, EVEX.LL0, EVEX.LLB; also illustrated with βββ)—aspreviously described, this field is context specific.

REX′ field 910—this is the remainder of the REX′ field and is theEVEX.V′ bit field (EVEX Byte 3, bit [3]-V′) that may be used to encodeeither the upper 16 or lower 16 of the extended 32 register set. Thisbit is stored in bit inverted format. A value of 1 is used to encode thelower 16 registers. In other words, V′VVVV is formed by combiningEVEX.V′, EVEX.vvvv.

Write mask field 970 (EVEX byte 3, bits [2:0]-kkk)—its content specifiesthe index of a register in the write mask registers as previouslydescribed. In one embodiment of the invention, the specific valueEVEX.kkk=000 has a special behavior implying no write mask is used forthe particular instruction (this may be implemented in a variety of waysincluding the use of a write mask hardwired to all ones or hardware thatbypasses the masking hardware).

Real Opcode Field 1030 (Byte 4) is also known as the opcode byte. Partof the opcode is specified in this field.

MOD R/M Field 1040 (Byte 5) includes MOD field 1042, Reg field 1044, andR/M field 1046. As previously described, the MOD field's 1042 contentdistinguishes between memory access and non-memory access operations.The role of Reg field 1044 can be summarized to two situations: encodingeither the destination register operand or a source register operand, orbe treated as an opcode extension and not used to encode any instructionoperand. The role of R/M field 1046 may include the following: encodingthe instruction operand that references a memory address, or encodingeither the destination register operand or a source register operand.

Scale, Index, Base (SIB) Byte (Byte 6)—As previously described, thescale field's 950 content is used for memory address generation. SIB.xxx1054 and SIB.bbb 1056—the contents of these fields have been previouslyreferred to with regard to the register indexes Xxxx and Bbbb.

Displacement field 962A (Bytes 7-10)—when MOD field 1042 contains 10,bytes 7-10 are the displacement field 962A, and it works the same as thelegacy 32-bit displacement (disp32) and works at byte granularity.

Displacement factor field 962B (Byte 7)—when MOD field 1042 contains 01,byte 7 is the displacement factor field 962B. The location of this fieldis that same as that of the legacy x86 instruction set 8-bitdisplacement (disp8), which works at byte granularity. Since disp8 issign extended, it can only address between −128 and 127 bytes offsets;in terms of 64 byte cache lines, disp8 uses 8 bits that can be set toonly four really useful values −128, −64, 0, and 64; since a greaterrange is often needed, disp32 is used; however, disp32 requires 4 bytes.In contrast to disp8 and disp32, the displacement factor field 962B is areinterpretation of disp8; when using displacement factor field 962B,the actual displacement is determined by the content of the displacementfactor field multiplied by the size of the memory operand access (N).This type of displacement is referred to as disp8*N. This reduces theaverage instruction length (a single byte of used for the displacementbut with a much greater range). Such compressed displacement is based onthe assumption that the effective displacement is multiple of thegranularity of the memory access, and hence, the redundant low-orderbits of the address offset do not need to be encoded. In other words,the displacement factor field 962B substitutes the legacy x86instruction set 8-bit displacement. Thus, the displacement factor field962B is encoded the same way as an x86 instruction set 8-bitdisplacement (so no changes in the ModRM/SIB encoding rules) with theonly exception that disp8 is overloaded to disp8*N. In other words,there are no changes in the encoding rules or encoding lengths but onlyin the interpretation of the displacement value by hardware (which needsto scale the displacement by the size of the memory operand to obtain abyte-wise address offset). Immediate field 972 operates as previouslydescribed.

Full Opcode Field

FIG. 10B is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the full opcodefield 974 according to one embodiment of the invention. Specifically,the full opcode field 974 includes the format field 940, the baseoperation field 942, and the data element width (W) field 964. The baseoperation field 942 includes the prefix encoding field 1025, the opcodemap field 1015, and the real opcode field 1030.

Register Index Field

FIG. 10C is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the register indexfield 944 according to one embodiment of the invention. Specifically,the register index field 944 includes the REX field 1005, the REX′ field1010, the MODR/M.reg field 1044, the MODR/M.r/m field 1046, the VVVVfield 1020, xxx field 1054, and the bbb field 1056.

Augmentation Operation Field

FIG. 10D is a block diagram illustrating the fields of the specificvector friendly instruction format 1000 that make up the augmentationoperation field 950 according to one embodiment of the invention. Whenthe class (U) field 968 contains 0, it signifies EVEX.U0 (class A 968A);when it contains 1, it signifies EVEX.U1 (class B 968B). When U=0 andthe MOD field 1042 contains 11 (signifying a no memory accessoperation), the alpha field 952 (EVEX byte 3, bit [7]-EH) is interpretedas the rs field 952A. When the rs field 952A contains a 1 (round952A.1), the beta field 954 (EVEX byte 3, bits [6:4]-SSS) is interpretedas the round control field 954A. The round control field 954A includes aone bit SAE field 956 and a two bit round operation field 958. When thers field 952A contains a 0 (data transform 952A.2), the beta field 954(EVEX byte 3, bits [6:4]-SSS) is interpreted as a three bit datatransform field 954B. When U=0 and the MOD field 1042 contains 00, 01,or 10 (signifying a memory access operation), the alpha field 952 (EVEXbyte 3, bit [7]-EH) is interpreted as the eviction hint (EH) field 952Band the beta field 954 (EVEX byte 3, bits [6:4]-SSS) is interpreted as athree bit data manipulation field 954C.

When U=1, the alpha field 952 (EVEX byte 3, bit [7]-EH) is interpretedas the write mask control (Z) field 952C. When U=1 and the MOD field1042 contains 11 (signifying a no memory access operation), part of thebeta field 954 (EVEX byte 3, bit [4]-S₀) is interpreted as the RL field957A; when it contains a 1 (round 957A.1) the rest of the beta field 954(EVEX byte 3, bit [6-5]-S₂₋₁) is interpreted as the round operationfield 959A, while when the RL field 957A contains a 0 (VSIZE 957.A2) therest of the beta field 954 (EVEX byte 3, bit [6-5]-S₂₋₁) is interpretedas the vector length field 959B (EVEX byte 3, bit [6-5]-L₁₋₀). When U=1and the MOD field 1042 contains 00, 01, or 10 (signifying a memoryaccess operation), the beta field 954 (EVEX byte 3, bits [6:4]-SSS) isinterpreted as the vector length field 959B (EVEX byte 3, bit[6-5]-L₁₋₀) and the broadcast field 957B (EVEX byte 3, bit [4]-B).

Exemplary Register Architecture

FIG. 11 is a block diagram of a register architecture 1100 according toone embodiment of the invention. In the embodiment illustrated, thereare 32 vector registers 1110 that are 512 bits wide; these registers arereferenced as zmm0 through zmm31. The lower order 256 bits of the lower16 zmm registers are overlaid on registers ymm0-16. The lower order 128bits of the lower 16 zmm registers (the lower order 128 bits of the ymmregisters) are overlaid on registers xmm0-15. The specific vectorfriendly instruction format 1000 operates on these overlaid registerfile as illustrated in the below tables.

Adjustable Vector Length Class Operations Registers InstructionTemplates A (FIG. 910, 915, zmm registers (the vector length is 64 thatdo not include the 9A; U = 0) 925, 930 byte) vector length field 959B B(FIG. 912 zmm registers (the vector length is 64 9B; U = 1) byte)Instruction templates B (FIG. 917, 927 zmm, ymm, or xmm registers (thethat do include the 9B; U = 1) vector length is 64 byte, 32 byte, or 16vector length field 959B byte) depending on the vector length field 959B

In other words, the vector length field 959B selects between a maximumlength and one or more other shorter lengths, where each such shorterlength is half the length of the preceding length; and instructionstemplates without the vector length field 959B operate on the maximumvector length. Further, in one embodiment, the class B instructiontemplates of the specific vector friendly instruction format 1000operate on packed or scalar single/double-precision floating point dataand packed or scalar integer data. Scalar operations are operationsperformed on the lowest order data element position in an zmm/ymm/xmmregister; the higher order data element positions are either left thesame as they were prior to the instruction or zeroed depending on theembodiment.

Write mask registers 1115—in the embodiment illustrated, there are 8write mask registers (k0 through k7), each 64 bits in size. In analternate embodiment, the write mask registers 1115 are 16 bits in size.As previously described, in one embodiment of the invention, the vectormask register k0 cannot be used as a write mask; when the encoding thatwould normally indicate k0 is used for a write mask, it selects ahardwired write mask of 0xFFFF, effectively disabling write masking forthat instruction.

General-purpose registers 1125—in the embodiment illustrated, there aresixteen 64-bit general-purpose registers that are used along with theexisting x86 addressing modes to address memory operands. Theseregisters are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI,RSP, and R8 through R15.

Scalar floating point stack register file (x87 stack) 1145, on which isaliased the MMX packed integer flat register file 1150—in the embodimentillustrated, the x87 stack is an eight-element stack used to performscalar floating-point operations on 32/64/80-bit floating point datausing the x87 instruction set extension; while the MMX registers areused to perform operations on 64-bit packed integer data, as well as tohold operands for some operations performed between the MMX and XMMregisters.

Alternative embodiments of the invention may use wider or narrowerregisters. Additionally, alternative embodiments of the invention mayuse more, less, or different register files and registers.

Exemplary Core Architectures, Processors, and Computer Architectures

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a CPU including one or more general purpose in-order coresintended for general-purpose computing and/or one or more generalpurpose out-of-order cores intended for general-purpose computing; and2) a coprocessor including one or more special purpose cores intendedprimarily for graphics and/or scientific (throughput). Such differentprocessors lead to different computer system architectures, which mayinclude: 1) the coprocessor on a separate chip from the CPU; 2) thecoprocessor on a separate die in the same package as a CPU; 3) thecoprocessor on the same die as a CPU (in which case, such a coprocessoris sometimes referred to as special purpose logic, such as integratedgraphics and/or scientific (throughput) logic, or as special purposecores); and 4) a system on a chip that may include on the same die thedescribed CPU (sometimes referred to as the application core(s) orapplication processor(s)), the above described coprocessor, andadditional functionality. Exemplary core architectures are describednext, followed by descriptions of exemplary processors and computerarchitectures.

Exemplary Core Architectures

In-Order and Out-of-Order Core Block Diagram

FIG. 12A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention. FIG.12B is a block diagram illustrating both an exemplary embodiment of anin-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention. The solid linedboxes in FIGS. 12A-B illustrate the in-order pipeline and in-order core,while the optional addition of the dashed lined boxes illustrates theregister renaming, out-of-order issue/execution pipeline and core. Giventhat the in-order aspect is a subset of the out-of-order aspect, theout-of-order aspect will be described.

In FIG. 12A, a processor pipeline 1200 includes a fetch stage 1202, alength decode stage 1204, a decode stage 1206, an allocation stage 1208,a renaming stage 1210, a scheduling (also known as a dispatch or issue)stage 1212, a register read/memory read stage 1214, an execute stage1216, a write back/memory write stage 1218, an exception handling stage1222, and a commit stage 1224.

FIG. 12B shows processor core 1290 including a front end unit 1230coupled to an execution engine unit 1250, and both are coupled to amemory unit 1270. The core 1290 may be a reduced instruction setcomputing (RISC) core, a complex instruction set computing (CISC) core,a very long instruction word (VLIW) core, or a hybrid or alternativecore type. As yet another option, the core 1290 may be a special-purposecore, such as, for example, a network or communication core, compressionengine, coprocessor core, general purpose computing graphics processingunit (GPGPU) core, graphics core, or the like.

The front end unit 1230 includes a branch prediction unit 1232 coupledto an instruction cache unit 1234, which is coupled to an instructiontranslation lookaside buffer (TLB) 1236, which is coupled to aninstruction fetch unit 1238, which is coupled to a decode unit 1240. Thedecode unit 1240 (or decoder) may decode instructions, and generate asan output one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decode unit 1240 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, look-up tables, hardware implementations,programmable logic arrays (PLAs), microcode read only memories (ROMs),etc. In one embodiment, the core 1290 includes a microcode ROM or othermedium that stores microcode for certain macroinstructions (e.g., indecode unit 1240 or otherwise within the front end unit 1230). Thedecode unit 1240 is coupled to a rename/allocator unit 1252 in theexecution engine unit 1250.

The execution engine unit 1250 includes the rename/allocator unit 1252coupled to a retirement unit 1254 and a set of one or more schedulerunit(s) 1256. The scheduler unit(s) 1256 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 1256 is coupled to thephysical register file(s) unit(s) 1258. Each of the physical registerfile(s) units 1258 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc. In one embodiment, the physical register file(s) unit1258 comprises a vector registers unit, a write mask registers unit, anda scalar registers unit. These register units may provide architecturalvector registers, vector mask registers, and general purpose registers.The physical register file(s) unit(s) 1258 is overlapped by theretirement unit 1254 to illustrate various ways in which registerrenaming and out-of-order execution may be implemented (e.g., using areorder buffer(s) and a retirement register file(s); using a futurefile(s), a history buffer(s), and a retirement register file(s); using aregister maps and a pool of registers; etc.). The retirement unit 1254and the physical register file(s) unit(s) 1258 are coupled to theexecution cluster(s) 1260. The execution cluster(s) 1260 includes a setof one or more execution units 1262 and a set of one or more memoryaccess units 1264. The execution units 1262 may perform variousoperations (e.g., shifts, addition, subtraction, multiplication) and onvarious types of data (e.g., scalar floating point, packed integer,packed floating point, vector integer, vector floating point). Whilesome embodiments may include a number of execution units dedicated tospecific functions or sets of functions, other embodiments may includeonly one execution unit or multiple execution units that all perform allfunctions. The scheduler unit(s) 1256, physical register file(s) unit(s)1258, and execution cluster(s) 1260 are shown as being possibly pluralbecause certain embodiments create separate pipelines for certain typesof data/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 1264). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 1264 is coupled to the memory unit 1270,which includes a data TLB unit 1272 coupled to a data cache unit 1274coupled to a level 2 (L2) cache unit 1276. In one exemplary embodiment,the memory access units 1264 may include a load unit, a store addressunit, and a store data unit, each of which is coupled to the data TLBunit 1272 in the memory unit 1270. The instruction cache unit 1234 isfurther coupled to a level 2 (L2) cache unit 1276 in the memory unit1270. The L2 cache unit 1276 is coupled to one or more other levels ofcache and eventually to a main memory.

By way of example, the exemplary register renaming, out-of-orderissue/execution core architecture may implement the pipeline 1200 asfollows: 1) the instruction fetch 1238 performs the fetch and lengthdecoding stages 1202 and 1204; 2) the decode unit 1240 performs thedecode stage 1206; 3) the rename/allocator unit 1252 performs theallocation stage 1208 and renaming stage 1210; 4) the scheduler unit(s)1256 performs the schedule stage 1212; 5) the physical register file(s)unit(s) 1258 and the memory unit 1270 perform the register read/memoryread stage 1214; the execution cluster 1260 perform the execute stage1216; 6) the memory unit 1270 and the physical register file(s) unit(s)1258 perform the write back/memory write stage 1218; 7) various unitsmay be involved in the exception handling stage 1222; and 8) theretirement unit 1254 and the physical register file(s) unit(s) 1258perform the commit stage 1224.

The core 1290 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.), including theinstruction(s) described herein. In one embodiment, the core 1290includes logic to support a packed data instruction set extension (e.g.,AVX1, AVX2), thereby allowing the operations used by many multimediaapplications to be performed using packed data.

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes separate instruction and data cache units1234/1274 and a shared L2 cache unit 1276, alternative embodiments mayhave a single internal cache for both instructions and data, such as,for example, a Level 1 (L1) internal cache, or multiple levels ofinternal cache. In some embodiments, the system may include acombination of an internal cache and an external cache that is externalto the core and/or the processor. Alternatively, all of the cache may beexternal to the core and/or the processor.

Specific Exemplary in-Order Core Architecture

FIGS. 13A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip. The logic blocks communicate through a high-bandwidthinterconnect network (e.g., a ring network) with some fixed functionlogic, memory I/O interfaces, and other necessary I/O logic, dependingon the application.

FIG. 13A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 1302 and with its localsubset of the Level 2 (L2) cache 1304, according to embodiments of theinvention. In one embodiment, an instruction decoder 1300 supports thex86 instruction set with a packed data instruction set extension. An L1cache 1306 allows low-latency accesses to cache memory into the scalarand vector units. While in one embodiment (to simplify the design), ascalar unit 1308 and a vector unit 1310 use separate register sets(respectively, scalar registers 1312 and vector registers 1314) and datatransferred between them is written to memory and then read back in froma level 1 (L1) cache 1306, alternative embodiments of the invention mayuse a different approach (e.g., use a single register set or include acommunication path that allow data to be transferred between the tworegister files without being written and read back).

The local subset of the L2 cache 1304 is part of a global L2 cache thatis divided into separate local subsets, one per processor core. Eachprocessor core has a direct access path to its own local subset of theL2 cache 1304. Data read by a processor core is stored in its L2 cachesubset 1304 and can be accessed quickly, in parallel with otherprocessor cores accessing their own local L2 cache subsets. Data writtenby a processor core is stored in its own L2 cache subset 1304 and isflushed from other subsets, if necessary. The ring network ensurescoherency for shared data. The ring network is bi-directional to allowagents such as processor cores, L2 caches and other logic blocks tocommunicate with each other within the chip. Each ring data-path is1012-bits wide per direction.

FIG. 13B is an expanded view of part of the processor core in FIG. 13Aaccording to embodiments of the invention. FIG. 13B includes an L1 datacache 1306A part of the L1 cache 1304, as well as more detail regardingthe vector unit 1310 and the vector registers 1314. Specifically, thevector unit 1310 is a 16-wide vector processing unit (VPU) (see the16-wide ALU 1328), which executes one or more of integer,single-precision float, and double-precision float instructions. The VPUsupports swizzling the register inputs with swizzle unit 1320, numericconversion with numeric convert units 1322A-B, and replication withreplication unit 1324 on the memory input. Write mask registers 1326allow predicating resulting vector writes.

FIG. 14 is a block diagram of a processor 1400 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention. The solidlined boxes in FIG. 14 illustrate a processor 1400 with a single core1402A, a system agent 1410, a set of one or more bus controller units1416, while the optional addition of the dashed lined boxes illustratesan alternative processor 1400 with multiple cores 1402A-N, a set of oneor more integrated memory controller unit(s) 1414 in the system agentunit 1410, and special purpose logic 1408.

Thus, different implementations of the processor 1400 may include: 1) aCPU with the special purpose logic 1408 being integrated graphics and/orscientific (throughput) logic (which may include one or more cores), andthe cores 1402A-N being one or more general purpose cores (e.g., generalpurpose in-order cores, general purpose out-of-order cores, acombination of the two); 2) a coprocessor with the cores 1402A-N being alarge number of special purpose cores intended primarily for graphicsand/or scientific (throughput); and 3) a coprocessor with the cores1402A-N being a large number of general purpose in-order cores. Thus,the processor 1400 may be a general-purpose processor, coprocessor orspecial-purpose processor, such as, for example, a network orcommunication processor, compression engine, graphics processor, GPGPU(general purpose graphics processing unit), a high-throughput manyintegrated core (MIC) coprocessor (including 30 or more cores), embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 1400 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 1406, and external memory(not shown) coupled to the set of integrated memory controller units1414. The set of shared cache units 1406 may include one or moremid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), orother levels of cache, a last level cache (LLC), and/or combinationsthereof. While in one embodiment a ring based interconnect unit 1412interconnects the integrated graphics logic 1408 (integrated graphicslogic 1408 is an example of and is also referred to herein as specialpurpose logic), the set of shared cache units 1406, and the system agentunit 1410/integrated memory controller unit(s) 1414, alternativeembodiments may use any number of well-known techniques forinterconnecting such units. In one embodiment, coherency is maintainedbetween one or more cache units 1406 and cores 1402-A-N.

In some embodiments, one or more of the cores 1402A-N are capable ofmulti-threading. The system agent 1410 includes those componentscoordinating and operating cores 1402A-N. The system agent unit 1410 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 1402A-N and the integrated graphics logic 1408.The display unit is for driving one or more externally connecteddisplays.

The cores 1402A-N may be homogenous or heterogeneous in terms ofarchitecture instruction set; that is, two or more of the cores 1402A-Nmay be capable of execution the same instruction set, while others maybe capable of executing only a subset of that instruction set or adifferent instruction set.

Exemplary Computer Architectures

FIGS. 15-18 are block diagrams of exemplary computer architectures.Other system designs and configurations known in the arts for laptops,desktops, handheld PCs, personal digital assistants, engineeringworkstations, servers, network devices, network hubs, switches, embeddedprocessors, digital signal processors (DSPs), graphics devices, videogame devices, set-top boxes, micro controllers, cell phones, portablemedia players, hand held devices, and various other electronic devices,are also suitable. In general, a huge variety of systems or electronicdevices capable of incorporating a processor and/or other executionlogic as disclosed herein are generally suitable.

Referring now to FIG. 15, shown is a block diagram of a system 1500 inaccordance with one embodiment of the present invention. The system 1500may include one or more processors 1510, 1515, which are coupled to acontroller hub 1520. In one embodiment the controller hub 1520 includesa graphics memory controller hub (GMCH) 1590 and an Input/Output Hub(IOH) 1550 (which may be on separate chips); the GMCH 1590 includesmemory and graphics controllers to which are coupled memory 1540 and acoprocessor 1545; the IOH 1550 couples input/output (I/O) devices 1560to the GMCH 1590. Alternatively, one or both of the memory and graphicscontrollers are integrated within the processor (as described herein),the memory 1540 and the coprocessor 1545 are coupled directly to theprocessor 1510, and the controller hub 1520 in a single chip with theIOH 1550.

The optional nature of additional processors 1515 is denoted in FIG. 15with broken lines. Each processor 1510, 1515 may include one or more ofthe processing cores described herein and may be some version of theprocessor 1400.

The memory 1540 may be, for example, dynamic random access memory(DRAM), phase change memory (PCM), or a combination of the two. For atleast one embodiment, the controller hub 1520 communicates with theprocessor(s) 1510, 1515 via a multi-drop bus, such as a frontside bus(FSB), point-to-point interface such as QuickPath Interconnect (QPI), orsimilar connection 1595.

In one embodiment, the coprocessor 1545 is a special-purpose processor,such as, for example, a high-throughput MIC processor, a network orcommunication processor, compression engine, graphics processor, GPGPU,embedded processor, or the like. In one embodiment, controller hub 1520may include an integrated graphics accelerator.

There can be a variety of differences between the physical resources1510, 1515 in terms of a spectrum of metrics of merit includingarchitectural, microarchitectural, thermal, power consumptioncharacteristics, and the like.

In one embodiment, the processor 1510 executes instructions that controldata processing operations of a general type. Embedded within theinstructions may be coprocessor instructions. The processor 1510recognizes these coprocessor instructions as being of a type that shouldbe executed by the attached coprocessor 1545. Accordingly, the processor1510 issues these coprocessor instructions (or control signalsrepresenting coprocessor instructions) on a coprocessor bus or otherinterconnect, to coprocessor 1545. Coprocessor(s) 1545 accept andexecute the received coprocessor instructions.

Referring now to FIG. 16, shown is a block diagram of a first morespecific exemplary system 1600 in accordance with an embodiment of thepresent invention. As shown in FIG. 16, multiprocessor system 1600 is apoint-to-point interconnect system, and includes a first processor 1670and a second processor 1680 coupled via a point-to-point interconnect1650. Each of processors 1670 and 1680 may be some version of theprocessor 1400. In one embodiment of the invention, processors 1670 and1680 are respectively processors 1510 and 1515, while coprocessor 1638is coprocessor 1545. In another embodiment, processors 1670 and 1680 arerespectively processor 1510 coprocessor 1545.

Processors 1670 and 1680 are shown including integrated memorycontroller (IMC) units 1672 and 1682, respectively. Processor 1670 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 1676 and 1678; similarly, second processor 1680 includes P-Pinterfaces 1686 and 1688. Processors 1670, 1680 may exchange informationvia a point-to-point (P-P) interface 1650 using P-P interface circuits1678, 1688. As shown in FIG. 16, IMCs 1672 and 1682 couple theprocessors to respective memories, namely a memory 1632 and a memory1634, which may be portions of main memory locally attached to therespective processors.

Processors 1670, 1680 may each exchange information with a chipset 1690via individual P-P interfaces 1652, 1654 using point to point interfacecircuits 1676, 1694, 1686, 1698. Chipset 1690 may optionally exchangeinformation with the coprocessor 1638 via a high-performance interface1692. In one embodiment, the coprocessor 1638 is a special-purposeprocessor, such as, for example, a high-throughput MIC processor, anetwork or communication processor, compression engine, graphicsprocessor, GPGPU, embedded processor, or the like.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 1690 may be coupled to a first bus 1616 via an interface 1696.In one embodiment, first bus 1616 may be a Peripheral ComponentInterconnect (PCI) bus, or a bus such as a PCI Express bus or anotherthird generation I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 16, various I/O devices 1614 may be coupled to firstbus 1616, along with a bus bridge 1618 which couples first bus 1616 to asecond bus 1620. In one embodiment, one or more additional processor(s)1615, such as coprocessors, high-throughput MIC processors, GPGPU's,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor, are coupled to first bus 1616. In one embodiment, second bus1620 may be a low pin count (LPC) bus. Various devices may be coupled toa second bus 1620 including, for example, a keyboard and/or mouse 1622,communication devices 1627 and a storage unit 1628 such as a disk driveor other mass storage device which may include instructions/code anddata 1630, in one embodiment. Further, an audio I/O 1624 may be coupledto the second bus 1620. Note that other architectures are possible. Forexample, instead of the point-to-point architecture of FIG. 16, a systemmay implement a multi-drop bus or other such architecture.

Referring now to FIG. 17, shown is a block diagram of a second morespecific exemplary system 1700 in accordance with an embodiment of thepresent invention. Like elements in FIGS. 16 and 17 bear like referencenumerals, and certain aspects of FIG. 16 have been omitted from FIG. 17in order to avoid obscuring other aspects of FIG. 17.

FIG. 17 illustrates that the processors 1670, 1680 may includeintegrated memory and I/O control logic (“CL”) 1672 and 1682,respectively. Thus, the CL 1672, 1682 include integrated memorycontroller units and include I/O control logic. FIG. 17 illustrates thatnot only are the memories 1632, 1634 coupled to the CL 1672, 1682, butalso that I/O devices 1714 are also coupled to the control logic 1672,1682. Legacy I/O devices 1715 are coupled to the chipset 1690.

Referring now to FIG. 18, shown is a block diagram of a SoC 1800 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 14 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 18, an interconnectunit(s) 1802 is coupled to: an application processor 1810 which includesa set of one or more cores 1402A-N, which include cache units 1404A-N,and shared cache unit(s) 1406; a system agent unit 1410; a buscontroller unit(s) 1416; an integrated memory controller unit(s) 1414; aset or one or more coprocessors 1820 which may include integratedgraphics logic, an image processor, an audio processor, and a videoprocessor; an static random access memory (SRAM) unit 1830; a directmemory access (DMA) unit 1832; and a display unit 1840 for coupling toone or more external displays. In one embodiment, the coprocessor(s)1820 include a special-purpose processor, such as, for example, anetwork or communication processor, compression engine, GPGPU, ahigh-throughput MIC processor, embedded processor, or the like.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code, such as code 1630 illustrated in FIG. 16, may be appliedto input instructions to perform the functions described herein andgenerate output information. The output information may be applied toone or more output devices, in known fashion. For purposes of thisapplication, a processing system includes any system that has aprocessor, such as, for example; a digital signal processor (DSP), amicrocontroller, an application specific integrated circuit (ASIC), or amicroprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMS) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), phase change memory(PCM), magnetic or optical cards, or any other type of media suitablefor storing electronic instructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

Emulation (Including Binary Translation, Code Morphing, Etc.)

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

FIG. 19 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 19 shows a program in ahigh level language 1902 may be compiled using an x86 compiler 1904 togenerate x86 binary code 1906 that may be natively executed by aprocessor with at least one x86 instruction set core 1916. The processorwith at least one x86 instruction set core 1916 represents any processorthat can perform substantially the same functions as an Intel processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel processor with at least onex86 instruction set core. The x86 compiler 1904 represents a compilerthat is operable to generate x86 binary code 1906 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 1916.Similarly, FIG. 19 shows the program in the high level language 1902 maybe compiled using an alternative instruction set compiler 1908 togenerate alternative instruction set binary code 1910 that may benatively executed by a processor without at least one x86 instructionset core 1914 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 1912 is used to convert the x86 binary code1906 into code that may be natively executed by the processor without anx86 instruction set core 1914. This converted code is not likely to bethe same as the alternative instruction set binary code 1910 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 1912 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 1906.

What is claimed is:
 1. An apparatus comprising: a decoder circuit todecode an instruction having fields for an opcode to define one of aplurality of potential arithmetic operations to perform, a first sourceoperand and a second source operand, and a destination operand; andexecution circuitry to execute the decoded instruction to perform,according to the opcode, the arithmetic operation on broadcasted packeddata elements of the first source operand and store results of eacharithmetic operation in the destination operand, wherein the packed dataelements of the first source operand to be broadcast are dictated byvalues of packed data elements stored in the second source operand,wherein the arithmetic operation is defined by the instruction, whereinat least some packed data elements of the first source operand are to bebroadcast multiple times, wherein to execute the decoded instruction,the execution circuitry is to, for each packed data element position ofthe destination operand, use data from each bit position ofcorresponding packed data element of the second source operand as anindex into a packed data element position of the first source operand,generate a result of the arithmetic operation of each value from eachindexed packed data element of the first source operand, and store theresult into the packed data element position of the destination operand.2. The apparatus of claim 1, wherein the first source operand is apacked data register and the second source operand is a memory location.3. The apparatus of claim 1, wherein the first source operand is apacked data register and the second source operand is a packed dataregister.
 4. The apparatus of claim 1, wherein the values of packed dataelements stored in the second source operand form a mask.
 5. Theapparatus of claim 1, wherein the arithmetic operation is one ofaddition, subtraction, multiplication, and division.
 6. The apparatus ofclaim 1, wherein the apparatus is to translate the instruction from afirst instruction set into an instruction of a second instruction setprior to a decode, wherein the instruction to be decoded is of thesecond instruction set.
 7. A method comprising: decoding an instructionhaving fields for an opcode to define one of a plurality of potentialarithmetic operations to perform, a first source operand and a secondsource operand, and a destination operand, and executing the decodedinstruction according to the opcode to sum broadcasted packed dataelements of the first source operand and store results of each sum inthe destination operand, wherein the packed data elements of the firstsource operand to be broadcast are dictated by values of packed dataelements stored in the second source operand, wherein at least somepacked data elements of the first source operand are broadcastedmultiple times, wherein executing the decoded instruction, the executioncircuitry is to, for each packed data element position of thedestination operand, use data from each bit position of correspondingpacked data element of the second source operand as an index into apacked data element position of the first source operand, generate aresult of the arithmetic operation of each value from each indexedpacked data element of the first source operand, and store the resultinto the packed data element position of the destination operand.
 8. Themethod of claim 7, wherein the first source operand is a packed dataregister and the second source operand is a memory location.
 9. Themethod of claim 7, wherein the first source operand is a packed dataregister and the second source operand is a packed data register. 10.The method of claim 7, wherein the values of packed data elements storedin the second source operand form a mask.
 11. The method of claim 7,wherein for each packed data element position of the destinationoperand, using data from each bit position of corresponding packed dataelement of the second source operand as an index into a packed dataelement position of the first source operand, generating a sum of eachvalue from each indexed packed data element of the first source operand,and storing the sum into the packed data element position of thedestination operand.
 12. The method of claim 7, wherein an initial valuefrom the destination is another input used in the sum generation. 13.The method of claim 7, further comprising: translating the instructionfrom a first instruction set into an instruction of a second instructionset prior to a decode, wherein the instruction to be decoded is of thesecond instruction set.
 14. A non-transitory machine-readable mediumstoring an instruction which when processed by a processor causes theprocessor to perform a method, the method comprising: decoding theinstruction having fields for an opcode to define one of a plurality ofpotential arithmetic operations to perform, a first source operand and asecond source operand, and a destination operand, and executing thedecoded instruction according to the opcode to sum broadcasted packeddata elements of the first source operand and store results of each sumin the destination operand, wherein the packed data elements of thefirst source operand to be broadcast are dictated by values of packeddata elements stored in the second source operand, wherein at least somepacked data elements of the first source operand are broadcastedmultiple times, wherein executing the decoded instruction, the executioncircuitry is to, for each packed data element position of thedestination operand, use data from each bit position of correspondingpacked data element of the second source operand as an index into apacked data element position of the first source operand, generate aresult of the arithmetic operation of each value from each indexedpacked data element of the first source operand, and store the resultinto the packed data element position of the destination operand. 15.The non-transitory machine-readable medium of claim 14, wherein thefirst source operand is a packed data register and the second sourceoperand is a memory location.
 16. The non-transitory machine-readablemedium of claim 14, wherein the first source operand is a packed dataregister and the second source operand is a packed data register. 17.The non-transitory machine-readable medium of claim 14, wherein thevalues of packed data elements stored in the second source operand forma mask.
 18. The non-transitory machine-readable medium of claim 14,wherein for each packed data element position of the destinationoperand, using data from each bit position of corresponding packed dataelement of the second source operand as an index into a packed dataelement position of the first source operand, generating a sum of eachvalue from each indexed packed data element of the first source operand,and storing the sum into the packed data element position of thedestination operand.
 19. The non-transitory machine-readable medium ofclaim 14, wherein an initial value from the destination is another inputused in the sum generation.
 20. The non-transitory machine-readablemedium of claim 14, further comprising: translating the instruction froma first instruction set into an instruction of a second instruction setprior to a decode, wherein the instruction to be decoded is of thesecond instruction set.